Throughout its Olympics coverage the BBC kept slipping in long trailers for its autumn schedules between events. The message was implicit: we know we're serving up a whole load of dross right now to anyone who isn't interested in sport, but stick with us and after the Games you will be in for untold treats. How quickly those promises are broken; when the highlight of the evening is a new series – the ninth – of Who Do You Think You Are? (BBC1), then you know the feelgood factor is already starting to flag.

When it started back in 2004, the genealogy series felt fresh, offering unusual insights into the backstories of well-known personalities; but now it all just seems rather formulaic and manipulative. We know there are going to be whoops of joy and tears of sadness, as the production team has already done its research and eliminated any celeb whose ancestry is just too dull for television. So rather than going on a journey of discovery into the past with someone, it feels more like being led by the nose into a number of contrived set-pieces.

Last night's episode had plenty of whoops and tears as Samantha Womack – best known as Ronnie Mitchell in EastEnders – found out that her great-grandfather had been jailed for nicking a cornet (the instrument, not the ice-cream) before being wounded in the first world war, and that her great-grandmother had been put in an orphanage after her mother went to America, but little sense of reward for anyone but her. Womack just isn't important enough to me to get emotionally involved with her great-grandparents for an hour. This isn't her fault, but it is a problem.

I also couldn't help feeling that the most fascinating aspects of Womack's life were to be found in her more recent past. What made her change her stage name from Samantha Janus to Samantha Womack? What part of her life did she want to forget? For a programme that trades on disappearance and reinvention, these seemed like reasonable questions to expect some answers to.

The Flowerpot Gang (BBC1) was nominally a brand new show, though it felt like one I had seen dozens of times before and wasn't in any hurry to see again – a hybrid of Challenge Anneka and Ground Force, in which Anneka Rice, looking so similar to how she did 20 years ago that I wondered if she was a hologram, reprised her role as the country's jolly hockey-sticks head girl. Joe Swift did the garden design, while Phil Tufnell came along for the ride and made a few jokes that were beyond feeble.

Over the course of the programme, the gang, along with some local volunteers, transformed the garden of a Sheffield care home for people with dementia into an accessible outdoor space, so it feels somewhat mean-spirited to be too critical. But it was a desperately dull hour of padded-out TV; the sort of programme that might just do as a Sunday afternoon filler, but had no place on a weekday primetime slot. Not that I want to deter television personalities from getting involved in worthwhile community projects; I would just rather they did so when there are no cameras around.

No matter how many documentaries I watch about the Nazi death camps, they never lose the power to shock, partly because of the subject matter but also because filmmakers are always looking for new ways to tell similar stories. Death Camp Treblinka: Survivor Stories (BBC4) gave a voice to the two remaining survivors, Kalman Taigman and Samuel Willenberg, of the 875,000 Jews and Gypsies who were sent to Treblinka in 1941-2. That they are both in their 80s and may not be around much longer only made their testimonies more compelling.

As so often, though, it was the passing details that had the most impact: Willenberg finding the coats of his two younger sisters among the personal effects of the dead he had been made to sort through by the Nazis; being asked by a wounded fellow escapee to kill him rather than let him be recaptured – and doing it. Unbearable. Perhaps the most disturbing footage, though, was the film shot by the Nazis themselves as a record of daily life in Treblinka – not for what it showed, so much as what it implied: that the Holocaust would one day be seen as something to be celebrated, not hidden.